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The Eventsourced library adds scalable actor state persistence and at-least-once message delivery guarantees to Akka. With Eventsourced, stateful actors: - Persist received messages by appending them to a log (journal) - Project received messages to derive current state - Usually hold current state in memory (memory image) - Recover current (or past) state by replaying received messages (during normal application start or after crashes) - Never persist current state directly (except optional state snapshots for recovery time optimization)

The ss command is used to show socket statistics. It can display stats for PACKET sockets, TCP sockets, UDP sockets, DCCP sockets, RAW sockets, Unix domain sockets, and much more. It allows showing information similar to netstat command. It can display more TCP and state information than other tools. It is a new, incredibly useful and faster (as compare to netstat) tool for tracking TCP connections and sockets. SS can provide information about: All TCP sockets. All UDP sockets. All established ssh / ftp / http / https connections. All local processes connected to X server. Filtering by state (such as connected, synchronized, SYN-RECV, SYN-SENT,TIME-WAIT), addresses and ports. All the tcp sockets in state FIN-WAIT-1 and much more. Most Linux distributions are shipped with ss and many monitoring tools. Being familiar with this tool helps enhance your understand of what's going on in the system sockets and helps you find the possible causes of a performance problem.

"Kiama is a Scala library for language processing. It enables convenient analysis and transformation of structured data. The programming styles supported by the library are based on well-known formal language processing paradigms, including attribute grammars, tree rewriting, abstract state machines, and pretty printing."

Dick Wall explores the state and future of Java, his reasons for switching to programming in Scala, the SubCut Dependency Injection library for Scala, Scala Compiler Plugins and much more.

"Datomic is a distributed database designed to enable scalable, flexible and intelligent applications, running on next-generation cloud architectures. It does this by: Bringing declarative data manipulation into the application, and the data with it Getting time, process and perception right Process (writes) require coordination Perception (reads) require none The past doesn't change Leveraging immutability, and a sound model of state Datomic has: ACID Transactions Joins A sound data model A logical query language - Datalog Thus, Datomic avoids the compromises and losses of many NoSQL solutions. In addition, it offers flexibility and power over the traditional model in supporting: Hierarchy Multi-valued attributes Minimal schema Reliable operation on unreliable, ephemeral cloud instances Time Datomic avoids manual caching and replication, complex configuration, sharding (automatic or manual), logging, locking, latching and disk management of traditional servers."

"Terraform is a tool for building, changing, and versioning infrastructure safely and efficiently. Terraform can manage existing and popular service providers as well as custom in-house solutions. Configuration files describe to Terraform the components needed to run a single application or your entire datacenter. Terraform generates an execution plan describing what it will do to reach the desired state, and then executes it to build the described infrastructure. As the configuration changes, Terraform is able to determine what changed and create incremental execution plans which can be applied. The infrastructure Terraform can manage includes low-level components such as compute instances, storage, and networking, as well as high-level components such as DNS entries, SaaS features, etc."

"Amazon EC2 Container Service (ECS) is a highly scalable, high performance container management service that supports Docker containers and allows you to easily run applications on a managed cluster of Amazon EC2 instances. Amazon ECS eliminates the need for you to install, operate, and scale your own cluster management infrastructure. With simple API calls, you can launch and stop container-enabled applications, query the complete state of your cluster, and access many familiar features like security groups, Elastic Load Balancing, EBS volumes, and IAM roles. You can use Amazon ECS to schedule the placement of containers across your cluster based on your resource needs and availability requirements. You can also integrate your own scheduler or third-party schedulers to meet business or application specific requirements."

"Flynn is two things: A "distribution" of components that out-of-the-box gives companies a reasonable starting point for an internal "platform" for running their applications and services. The banner for a collection of independent projects that together make up a toolkit or loose framework for building distributed systems. Flynn is both a whole and many parts, depending on what is most useful for you. The common goal is to democratize years of experience and best practices in building distributed systems. It is the software layer between operators and developers that makes both their lives easier. Unlike most PaaS's, Flynn can run stateful services as well as 12 factor apps. This includes built-in database appliances (just Postgres to start). Flynn is modular so users can easily modify, upgrade, and replace components. "

"Deis (pronounced DAY-iss) is an open source PaaS that makes it easy to deploy and manage applications on your own servers. Deis builds upon Docker and CoreOS to provide a lightweight PaaS with a Heroku-inspired workflow. Deis can deploy any application or service that can run inside a Docker container. In order to be scaled horizontally, applications must follow Heroku's 12-factor methodology and store state in external backing services."

"MaestroNG, an orchestrator of Docker-based deployments. The original Maestro was developed as a single-host orchestrator for Docker-based deployments. Given the state of Docker at the time of its writing, it was a great first step towards orchestration of deployments using Docker containers as the unit of application distribution. Docker having made significant advancements since then, deployments and environments spanning across several hosts are becoming more and more common and are in the need for some orchestration. Based off ideas from the original Maestro and taking inspiration from Docker's links feature, MaestroNG makes the deployment and control of complex, multi-host environments using Docker containers possible and easy to use. Maestro of course supports declared dependencies between services and makes sure to honor those during environment bring up. MaestroNG is, for now, a command-line utility that allows for automatically managing the orchestrated deployment and bring up of a set of service instance containers that compose an environment on a set of target host machines."

"Terraform is a tool for building, changing, and versioning infrastructure safely and efficiently. Terraform can manage existing and popular service providers as well as custom in-house solutions. Configuration files describe to Terraform the components needed to run a single application or your entire datacenter. Terraform generates an execution plan describing what it will do to reach the desired state, and then executes it to build the described infrastructure. As the configuration changes, Terraform is able to determine what changed and create incremental execution plans which can be applied. The infrastructure Terraform can manage includes low-level components such as compute instances, storage, and networking, as well as high-level components such as DNS entries, SaaS features, etc. The key features of Terraform are: Infrastructure as Code: Infrastructure is described using a high-level configuration syntax. This allows a blueprint of your datacenter to be versioned and treated as you would any other code. Additionally, infrastructure can be shared and re-used. Execution Plans: Terraform has a "planning" step where it generates an execution plan. The execution plan shows what Terraform will do when you call apply. This lets you avoid any surprises when Terraform manipulates infrastructure. Resource Graph: Terraform builds a graph of all your resources, and parallelizes the creation and modification of any non-dependent resources. Because of this, Terraform builds infrastructure as efficiently as possible, and operators get insight into dependencies in their infrastructure. Change Automation: Complex changesets can be applied to your infrastructure with minimal human interaction. With the previously mentioned execution plan and resource graph, you know exactly what Terraform will change and in what order, avoiding many possible human errors."

"What is Aurora? Platforms like Twitter operate across tens of thousands of machines, with hundreds of engineers deploying software daily. In this type of environment, automation is critical. Aurora is software that keeps services running in the face of many types of failure, and provides engineers a convenient, automated way to create and update these services. To accomplish this, Aurora leverages the Apache Mesos cluster manager, which provides information about the state of the cluster. Aurora uses that knowledge to make scheduling decisions. For example, when a machine experiences failure Aurora automatically reschedules those previously-running services onto a healthy machine in order to keep them running."

"Terrier is a highly flexible, efficient, and effective open source search engine, readily deployable on large-scale collections of documents. Terrier implements state-of-the-art indexing and retrieval functionalities, and provides an ideal platform for the rapid development and evaluation of large-scale retrieval applications."

"ImageTerrier is an open-source, scalable, high-performance search engine platform for content-based image retrieval applications. The ImageTerrier platform provides a comprehensive test-bed for experimenting with image retrieval techniques. The platform incorporates a state-of-the-art implementation of the single-pass indexing technique for constructing inverted indexes and is capable of producing highly compressed index data structures. ImageTerrier is written as an extension to the open-source Terrier test-bed platform for textual information retrieval research."

"WireGuard is an extremely simple yet fast and modern VPN that utilizes state-of-the-art cryptography. It aims to be faster, simpler, leaner, and more useful than IPSec, while avoiding the massive headache. It intends to be considerably more performant than OpenVPN."